Scholarly reference sources can give you a jumpstart into your research by summarizing themes or schools of thought, offering statistical compilations, or listing key publications.
Want something more substantial than Wikipedia? These standard history series offer more than fast food:
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Encyclopedia of Historians and Historical Writing
Companion to Historiography
Dictionary of Concepts in History
Great Historians from Antiquity to 1800 by 
Great Historians of the Modern Age by This link opens in a new window This link opens in a new window This link opens in a new window This link opens in a new window This link opens in a new windowA good subject bibliography can save you time by suggesting key publications on a topic; sometimes abstracts or summaries of those publications are also offered
Caveat Lector: As soon as a bibliography is published, it is out of date. Scholarship marches on! So be sure to update your secondary sources by searching book catalogs and article databases for the most recent studies.
The American Historical Association's Guide to Historical Literature
Arkansas History: An Annotated Bibliography
The Harvard Guide to African-American history
The American Civil War: A Handbook of Literature and Research
American Foreign Relations since 1600 by These sources will provide articles by authorities in the field on topics, events, places, and persons. Articles will range in length from one or two paragraphs to dozens of pages. Most will give a bibliography of recommended books and articles for further research. There are hundreds of specialized subject encyclopedias. Look in OneSearch under keyword “encyclopedias” + your topic to find more.
Dictionary of the History of Ideas
Brill's New Pauly:
Dictionary of the Middle Ages This link opens in a new window
Encyclopedia of Latin American History and Culture
Encyclopedia of Africa South of the Sahara
Encyclopedia of Modern Asia
Handbook of North American Indians